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Pollen
Mon Feb 28, 2005
Listen in RealAudio 
Aaachoo! Sneezes at this time of year probably aren’t due to hay fever. But soon… Hi, I’m Bryan Yeaton for The Weather Notebook.
The term hay fever arose several centuries ago when many people who lived and worked on farms felt ill during haying time. They sneezed terribly; their noses ran; their eyes itched and swelled. Most were convinced the hay, or perhaps the hot weather, had made them sick. Finally in 1873, Englishman Charles Blackley associated the condition with plant pollens.
Hay fever is not really a fever since sufferers don’t run a temperature. It’s also misleading because hay has little to do with it. Technically, these warm-weather allergies are called allergic rhinitis, which means “inflammation of the nose,” or, the sinuses.
Hay fever arises in early summer with the maturing of grasses. It continues from early August until the first hard freeze, complements of many weed species, particularly ragweed, to which 75 percent of hay-fever sufferers are sensitive. Cross-reactivity among these pollens ensures that a reaction to one will almost certainly cause reactions to all.
These weeds produce copious amounts of pollen designed to be dispersed by the wind. The warm, dry, breezy days common in late summer and early fall provide optimal weather for pollen to be spread over wide areas, as the little devils rise high on ascending air currents. Pollen counts vary during the day as the diurnal weather cycle unfolds in concert with pollen production.
Rain usually relieves allergy symptoms because it literally washes pollens out of the air. But for allergy sufferers, the real relief comes with the cold temperatures, as old Jack Frost closes the pollen factories for another year.
Thanks to our contributing writer, meteorologist Keith Heidorn. Our show is underwritten by Subaru of America, and produced by the Mount Washington Observatory.
Today's Links
Aeroallergens: Misery Blowin\' In The Wind
http://www.islandnet.com/~see/weather/almanac/arc2001/alm01aug.htm
Aerobiology Research Laboratories: Pollen Allergen
http://www.pollenplus.com/pollen/index.html
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